Electro-optical signaling



April .25, 1939; rscHROTER ELEGTRO OPTIGAL S IGNALING Filled Sept. 29, 193e- SUI/RH 0F RE ENERGY R .H RF. Y OW We 0 W MEN w A m Y B Patented Apr. 25, 1 939 PATENT OFFICE ELECTED-OPTICAL SIGNALING Fritz Schriite'r, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. IL, Berlin, Germany, a corporation of Germany Application September 29,1936, Serial No. 103,083

In Germany September 24, 1935 7 Claims.

This invention relates to electro-optical signaling and, in particular, to facsimile in television systems embodying actino-dielectric effect transmitters.

It is well known that certain luminescent materials have the property of changing their dielectric constant upon exposure to light and has been reported both in Annalen der Physik Volume 28, pages 490 et seq. for the year 1909 by Lenard, and Der Handbuch der Experimental Physik Volume 23, Part I by Wien and Harms, 1928, pages 213 through 245. This phenomena, known by the term actino-dielectric effect while definite and stable, does not lend itself readily to be used in practice in view of the comparatively small change which takes place.

Accordingly, .one of the objects of this invention is to provide ways and means to utilize practically the actino-dielectric effect of luminescent materials. This efiect can be used efiicaciously in television and facsimile systems for transmitting various types of subject matter, and in particular, is adapted to be used wherever it is desired to convert optical phenomena into electrical phenomena.

Accordingly, another object of my invention is to provide new ways and means of converting optical phenomena into electrical phenomena.

Another object of my invention is to provide an electro-optical transmitting system which has improved properties.

Other and ancillary objects will become apparent both to the public and those skilled in the art upon a reading of the specification taken together with the drawing.

In the drawing, Fig. l is a schematic illustration representing one form of my invention; and

Figs. 2 and 3 show a perspective and plan view of another embodiment of my invention.

In Fig. 1 a layer of luminescent material I is positioned between a plate electrode H and a coarse mesh-like electrode |2 forming a condenser in which the luminescent layer In serves as a dielectric. This condenser is inserted in one branch of the bridge circuit whose other branches contain the variable condenser l3 and the fixed condensers I4 and IS. The junction points between the actino-dielectric cell and the condenser l3 and between the fixed condensers l4 and I5, have connected through the means of the terminal IS, a source of radio frequency energy 4|. The other junction points of the bridge are connected to the deflection plates ll of a cathode ray tube IS. The cathode ray tube is shown only schematically with its cathode 20 and an apertured diaphragm 2|,-it being understood, of course, that a suitable electron lens is interposed between the cathode 20 and the deflecting plates I! to focus the electrons emitted from the cathode 20 into a narrow beam. When the bridge is balanced, i. e. no potential fed to the deflecting plates II, the cathode ray beam originating at the cathode 20 passes through the aperture in the diaphragm 2|. In operation, for example, in a facsimile system, a source of light 30 is focused into a fine spot of light upon a drum 33 by means of an optical system 3|. The reflected light is picked up by another optical system 35 and is reflected upon the actino-dielectric cell, comprising the two electrodes II and I2, and the dielectric layer l0 between them. The bridge is balanced for any predetermined intensity of light falling upon the cell43 as, for example, for zero illumination. To balance the bridge it is only necessary under these conditions with no light reaching the cell 43, to vary the capacity of the condenser I3 so that no radio frequency potential exists between the two junction points connected to the deflecting plates l1. Under these conditions the cathode ray passes through the aperture of the diaphragm 2|. If, however, light is now permitted to fall on the cell 43, the equilibrium of the bridge will be destroyed so that an alternating current potential will appear between the upper and lower junction points of the bridge which, in turn, deflects the cathode ray back and forth across the aperture. fore, will move acrossthe diaphragm 2| at the frequency of the alternating current source 4| and with an amplitude depending upon the magnitude of the unbalanced potential difierence appearing across the junction points, which are connected to the plates II.

It will be appreciated that since the frequency is fixed, the amplitude of the swing will determine the duration during which the cathode ray will pass through the aperture in the diaphragm 2|, and accordingly, therefore, the number of electrons per unit time which will pass through the aperture will vary in accordance with the intensity of the light upon the cell 43. Beyond the diaphragm 2|-may be arranged a suitable secondary emission type of amplifier, or if desired, a single collecting electrode which may be connected to a suitable conventional amplifier for amplifying the cathode ray current received upon the electrode. The output of either of these The ray, theretypes of amplifiers may then be used for trans- 5 mission of the electro-optical signal. It will be readily apparent that this type of bridge circuit makes possible the eflicacious use of an actinodielectric cell which is both practical, stable and simple.

In Figs. 2 and 3 shown, another method'by which the actino-dielectrlc effect" can be utilized for transmission of electro-optical signals is shown. .Fig. 2 shows such an arrangement in perspective.

Two electrodes 22 and 23 are arranged parallel to each other and connected through terminals I6 to a source of radio frequency energy 4|. The electrode 22 has the surface facing the electrode 23 coated with a luminescent material 24. The object to be transmitted is represented by the plane 39 and a suitable optical system 31 projects the object upon the luminescent surface 24 of the electrode 22. A suitable apertured diaphragm 45 serves to provide only a single line of the object being projected upon the luminescent surface 24. Suitable means, of course, would be provided in the case of a record larger than a single line for moving either the diaphragm or the object so as to continually scan the subject to be transmitted. Between these two plates a concentrated cathode ray 25 is deflected back and forth and beyond the two plates anarrow apertured diaphragm 41 is provided.

It will be immediately appreciated that the cathode ray in passing between the two electrodes 22 and 23 will be deflected, in accordance with the intensity of illumination provided from the exposure of the illumination upon the luminescent material 24. Accordingly, therefore, the number of electrons that pass through the aperture 26 in the diaphragm 41 will be in accordance with the intensity of illumination on the elemental areas of the luminescent material 24. These elemental areas would comprise rectangles of vanishing small widths and whose length is determined by the width of the luminescent material 24. The cathode ray 25 which, in the course of scanning of a line, is moved horizontally past the luminescent layer 24, is thus subjected in its travel to an intensity of a deflecting field, depending upon the intensity of exposure of the respective strip element, and therefore, the ray will be moved to and fro across the aperture 26 with the frequency of the alternating current source IS in the direction of the arrow P. The

electron current passing through the aperture 26 of the diaphragm 4! thus will be varied in accordance with the distribution of brightness along the image light charges projected upon the luminescent layer 24. Beyond the apertured diaphragm 41 a secondary emission amplifier or a collecting electrode with a suitable conventional amplifier connected thereto may be provided as explained above.

It will be appreciated, of course, that the showings in both Figs. 2 and 3 are intended merely to represent the disposition of the new electrodes electrical signaling impulses, which comprises the steps of actino-dielectrically producing potential variations in accordance with the varying light intensities, producing a beam of electrons. controlling the produced beam of electrons by the produced potential variations to vary the number 1 of electrons in the beam reaching a predetermined point, collecting the electrons reaching the predetermined polnt, and producing electrical signaling impulses of an amplitude proportional to the number of collected electrons.

2. In an electro-optical signaling system, the method of converting varying light intensities representative of an image to be transmitted into electrical signaling impulses which comprises the steps of actino-dielectrically producing potential variations in accordance with the varying light intensities, producing a beam of electrons, deflecting the produced beam of electrons by the produced potential variations to vary the number of electrons in the beam reaching a predetermined point, collecting the electrons reaching the predetermined point, and producing electrical signaling impulses of an amplitude proportional to the number of collected electrons.

3. An electro-optical signaling system for converting varying light intensities representative of an object to be transmitted which comprises means for actino-dielectrically producing potential variations in accordance with the varying light intensities, means for producing a beam of electrons, means for controlling the produced beam of electrons by the produced potential variations to vary the number of electrons in the beam reaching the predetermined point, means for collecting the electrons reaching the predetermined point, and means for producing electrical signaling impulses of an amplitude proportional to the number of collected electrons.

4. An eIectro-optical signaling system for converting varying light intensities representative of an object to be transmitted which comprises means for actino-dielectrically producing potential variations in accordance with the varying light intensities, means for producing a beam of electrons, means for deflecting the produced beam of electrons by the produced potential variations to vary the number of electrons in the beam reaching a predetermined point, means for collecting the electrons reaching the predetermined point, and means for producing electrical signaling impulses of an amplitude proportional to the number of collected electrons.

5. An electro-optical system for converting varying light intensities representative of an object to be transmitted which comprises an electrical bridge having three capacitive arms and an actino-dielectric cell in the fourth arm, means to supply radio frequency energy to one diagonal of the bridge, means to project elemental areas of an image of the object to be transmitted upon the actino-dielectric cell, a cathode ray tube having means to project a beam of electrons along a predetermined path, an apertured diaphragm normal to the predetermined path, a pair of defleeting plates intermediate the means for projecting the beam of electrons and the apertured diaphragm, and connections from the other diagonal of the bridge to the deflecting plates whereby varying light intensities falling on the actinodielectric cell deflect the beam of electrons to vary the number of electrons passing through the apertured diaphragm.

6. An electro-optical system for converting varying light intensities representative of an object to be transmitted which comprises a cathode ray tube having means to project a beam of electrons along a predetermined path, a deflecting electrode system for deflecting said beam of electrons, said deflecting electrode system comprising a planar metal plate having a coating of actino-dielectric material thereon, said deflecting electrode system being positioned with respect to the path of the electrons with the actinodielectric material facing the path, an apertured diaphragm positioned beyond the deflecting electrode system, means to supply radio frequency energy to the deflecting electrode system, and

means to project light upon the actino-dielectric '7. A deflecting electrode system for a cathode ray tube comprising a pair of planar parallel plates, and a, layer of actino-dielectric material supported upon one of the surfaces of the plates, said surface facing the other of said plates. 

